This invention relates to a live roller conveyor, that is, a conveyor comprising a plurality of rollers which form a conveying surface for an article placed on the conveyor, at least some of the rollers being driven by a drive means.
More particularly, the invention relates to a live roller conveyor in which the drive means comprises a drive shaft which extends transverse to the rollers generally along the conveyor in the direction in which the articles are conveyed, drive belts being engaged with the drive shaft and the driven rollers to transmit drive from the drive shaft, which in use is rotated about its longitudinal axis, to the driven rollers.
Such a conveyor will hereinafter be referred to as being "of the kind specified".
Conventionally, conveyors of the kind specified comprise side frame members between which the rollers extend, the side frame members being interconnected by cross braces for rigidity. The drive shaft is mounted below the cross braces and is journaled in bearings which are secured to the undersides of at least some of the cross braces. Such a construction suffers from at least the following disadvantages.
It will be appreciated that, in use, the belts which extend between the drive shaft and the driven rollers wear and after a given time, require replacement. The replacement belts have to be fed along the drive shaft from one end. In a conventional construction this requires the bearings to be dismantled from the cross braces which disturbs the alignment of the drive shaft. Further, because the drive shaft is mounted beneath the cross braces, this dismantling has to be carried out from beneath the conveyor as does all maintenance work on the bearings, which is obviously difficult and inconvenient.
An object of the present invention is to provide a new or improved conveyor of the kind specified which overcomes or reduces the above mentioned problems.
According to one aspect of the invention we provide a conveyor of the kind specified wherein the drive shaft is mounted beneath the rollers and above a plane containing the lowermost point or points of the cross braces.
Thus access to the drive shaft can be obtained from above the conveyor, although it may be necessary to remove one or more of the rollers from the conveyor before maintenance procedures can be carried out. However the rollers are conveniently mounted so as to be readily removable from the conveyor to facilitate belt replacement, and hence this presents no problem.
Preferably, each of the cross braces has a downwardly extending slot which opens to the top of the cross brace. The drive shaft may be received in the slots and be mounted for rotation about an axis between the plane containing the lowermost point or points of the cross braces and another plane containing the uppermost point or points of the cross braces.
Alternatively, the cross braces or some of the cross braces may carry mountings which receive the drive shaft so that the drive shaft is located for rotation about an axis which lies beneath the rollers but about a plane containing the uppermost point or points of the cross braces.
The cross braces or at least some of the cross braces may carry a bearing in which the drive shaft is journaled for rotation. Preferably, all of the cross braces carry such a bearing.
In a preferred embodiment, where the cross braces each have a slot opening to the top, the bearings are bolted or otherwise releasably fastened to the cross braces around the periphery of the respective slot.
The clearance between the slots of the cross braces and the drive shaft, when the bearing is dismantled, is preferably sufficiently large to enable a replacement belt or belts to be threaded past.
In such a construction, it has been found that worn drive belts can be replaced without disturbing the alignment of the drive shaft because only one bearing needs to be dismantled from engagement with its respective cross brace at a time, the bearing being re-secured to the respective cross brace when the or each replacement belt has been threaded past, before the next bearing is dismantled.
Each bearing preferably comprises at least two housing parts, the two housing parts being secured together and to the respective cross brace by a common fastening means. Thus in dismantling the bearing from engagement with its respective cross brace, the housing parts of the bearing are also readily separable.
Preferably each bearing also comprises a hub part which, in use, is interposed between the two housing parts, the hub carrying at least an inner bearing race which rotates with the drive shaft relative to an outer bearing race which may be provided by the hub, or by one or both of the housing parts. The housing parts may each have an opening in which the hub part is received, the clearance between a wall of the opening and the drive shaft being sufficient to enable a drive belt to be threaded therethrough. Thus one or more replacement drive belts can be threaded along the drive shaft through the openings in the housing parts, over the hub part, and through the respective slot in the cross brace, to a desired position along the drive shaft.
Alternatively where the drive belt is sufficiently large and/or the exterior dimensions of the housing parts are sufficiently small, the belt may simply be passed over the housing parts and over the hub to a desired position along the drive shaft.
The circumferential mating surfaces of the hub and the two housing parts are preferably part-spherical so that the hub can become misaligned within the housing parts without deterimentally affecting the efficiency of the bearing. This is particularly an advantage on bend conveyor sections when the drive shaft may not extend at exactly 90.degree. to the cross braces.
The housing part, which in use is nearest the cross member, may be made by molding, for example, a plastics material. It has been found that in such a construction, noise levels are reduced as the drive shaft rotates.
The drive shaft may comprise a plurality of pulleys with which the drive belts are engaged.
The conveyor may comprise a plurality of conveyor sections each having its own drive shaft and associated bearings, cross braces, and conveyor side frame members and rollers, the drive shaft of each section being coupled to the drive shaft of another section to enable drive to be transmitted along the conveyor. Drive shafts may be coupled by coupling means which enable the drive shaft to transmit power to another conveyor section, and/or to receive power from another conveyor section.
The conveyor sections may be straight, in which case the rollers are all parallel to one another, and the drive shaft may extend generally perpendicular to the axes of rotation of each of the rollers, or the conveyor may include a bend section, in which case the axes of rotation of some of the rollers may be arranged transverse to the axes of rotation of others of the rollers and to the drive shaft.
According to a second aspect of the invention, we provide a bearing for use with a conveyor according to the first aspect of the invention, the bearing comprising at least two housing parts and a hub, the hub carrying an inner bearing race which in use rotates with a shaft journaled in the bearing, the housing parts each having an opening to enable the hub to be interposed between the housing parts, the hub, or one or both of the housing parts, carrying an outer bearing race.
The hub preferably has a collar which extends axially along the drive shaft beyond the or one of the housing parts when the housing parts are assembled, the collar being adapted to be received in an opening in a mounting.
The mounting may comprise a cross brace of a conveyor in accordance with the first aspect of the invention, the opening in the cross brace comprising a slot which extends downwardly from the top of the cross brace.
The shaft journaled in the bearing may comprise a drive shaft of the conveyor.
Preferably, when the housing parts are separated from the hub part, there is adequate clearance between the shaft and the periphery of the opening in each housing part, to enable a drive belt to be threaded therethrough. The drive belt may be threaded over the hub which is preferably of smaller diameter than the housing parts. Alternatively the exterior dimensions of the housing parts of the drive belt may be such that the drive belt may be passed over the housing parts.
The hub may comprise inner and outer bearing races with rolling elements such as ball bearings or rollers between the races. The circumferential mating surfaces of the housing parts and the outer bearing race of the hub may be part-spherical.